Significant advances in recent years in the reduction in physical size and cost of electronic circuits have resulted from improvements in techniques for the manufacture of microelectronic circuits, e.g. microlithography. In general, microlithography comprises applying a film of a radiation-sensitive polymeric material, i.e. a resist medium, to one surface of a substrate, irradiating selected portions of the film with, e.g. ultraviolet light, an electron beam, X-ray or the like, and developing the film with a solvent to remove solubilized portions thereof. In the instance of a positive resist, the portions of the film irradiated become more soluble in the developer solvent than non-irradiated portions. The resist medium remaining on the surface of the substrate is then employed as a protective mask to facilitate the selective etching or other treatment of the exposed portions of the substrate.
Etching of the substrate may be conventionally carried out by chemical treatment or by plasma discharge. Plasma etching, generally, affords finer resolution than chemical etching and is additionally advantageous in that it is free of the pollution and handling problems inherent in the use of chemical etchants. Many resist materials, however, cannot withstand plasma discharge and are eroded along with the substrate, resulting in complete loss of pattern definition. Therefore, chemical etching is more commonly used in spite of the above-named disadvantages.
There is a continuing search for polymeric materials with increased sensitivity to radiation such as electron beam radiation to achieve higher resolution in answer to the demand for ever-finer circuitry. The poly(olefin sulfones) are a major group of resist media described in the literature. Although a significant number of poly(olefin sulfones) are known to those of ordinary skill in the art, only one, i.e. poly(1-butenesulfone), is commercially available. Although a sensitive resist medium, this material is disadvantageous in that: it does not adhere well to certain substrates, particularly chromium; it must be exposed at an electron beam dose of 1 .mu.C/cm.sup.2 which is at or near the capacity of the irradiation apparatus in many installations; and it has poor resistance to plasma etching.
In accordance with this invention, there is provided a positive electron beam recording media which has increased sensitivity in comparison with poly(1-butenesulfone) and which possesses excellent adherence to chromium.